Control devices for hydraulic actuators



y 1960 J. 1,. GRATZMULLER 2,938,346

CONTROL DEVICES FOR HYDRAULIC ACTUATORS Filed Aug. 5, 1958 United States Patent D F 2,938,346 r I CONTROL DEVICES FORHYDRAULI ACTUATORS Jean Louis Gratzmuller, 66 Blvd, Maurice Barres,

Neuilly-sur-Seiue, France 1 Filed Aug. 5, 1958, Ser'. No. 753,357 Claims priority, application France Aug. '12, 195 7 Claims. (Cl. 6051) f actuators. More particularly, this inventionrelates to devices for controlling the connection of a single acting hydraulic jack or like actuator'to a hydraulic pressure source and to an exhaust respectively. The connection is effected 'so that both the power and return strokes of the actuator (the latter being effected by continuously acting biasing means, e.g. a spring or weight)- can be initiated by a triggering action and thereafter completed automatically. On completion of either stroke, the movable member of the actuator is positively maintained in its terminal positions by hydraulic pressure or. by the biasing means, respectively until another triggering action is performed.

Devices of this kind are especially adapted for controlling an hydraulic actuator which operates an electrical circuit-breaker meeting certain requirements. In such a circuit breaker, it is necessary for the closing and opening movements of which, when once initiated, must becompleted without fail, and the circuit-breaker must thereafter he held positively in the closed or open'position as the case may be until it is required intentionally to open or close the circuit-breaker respectively. Moreover, the opening movement must be effected as rapidly as possible to facilitate arc-quenching, and consequently it is usual for the opening movement to be performed by the return stroke of the actuator. The permanent bias means effects the return stroke of the actuator by exerting a very strong effort, provision being made for exhausting the actuator extremely rapidly.

A control device of the kind above defined is described in the United States Patent 2,900,960 for Hydraulic Control Device and fulfils the requirement of positively holding the actuator by continued application of the supply pressure in the terminal position of its power stroke. However, it is possible in certain circumstances that vibrations and chattering may occur at the beginning of the power stroke of the actuator. This is particularly the situation if the triggering action, by which the power stroke is initiated, is discontinued before the necessary operative'pressure has been built-up in the service line that feeds the actuator.

The main object of this invention is to provide means for eliminating this kind of malfunctioning.

A more particular object of this invention is to provide a control device of the type first herein defined which comprises a chamber communicating with the actuator and also communicating through a normally closed main valve with the pressure source and with exhaust through an auxiliary valve, which, when closed, positively opens the main valve.

Accordingly, means are provided for continuously applying the pressure in the chamber to the auxiliary valve in the sense to close it, the auxiliary valve being also subjected when closed to the same pressure, but with consid-. erably reduced effort, in the sense to open it. A first triggering valve is provided for temporarily applying the 7 2,938,346 Patented May 31, 1960 and a calibrated restrictor is provided which is operative between the chamber andthe actuator.

Normally the main" valve is'closedand the auxiliary valve is open and the actuator is vented to exhaust through the auxiliary valve and the chamber, hereinafter referred to as the intermediate chamber. The bias means therefore holds the actuator in the end of return stroke posi- 10 This invention relates to control devices for hydraulic Y pressure of the source to the auxiliary valve in'the sense 5 auxiliary valve to initiate opening thereof when closed,

tion, until the power stroke is triggered by opening the first triggering valve to close the auxiliary valve and open the main valve. When the first triggering valve closes, the closing pressure on the auxiliary valve is that in the intermediate chamber and is supplied from the pressure source through the main valve. As long as flow is taking place through the main valve this closing pressure is less than the supply pressure owing to the pressure-drop through the main valve. If the intermediate chamber were in free communication with the actuator, then this pressure-drop would account for substantially the whole of the difference between the supply pressure and the pressure in the actuator. Further, if the first triggering valve were allowed to close prematurelyduring the time interval required to build-up the pressure in the actuator to an operating pressure sufncient to overcome the effort of the return bias means, then the pressure downstream of the main valve in the intermediate chamber might not be sufiicient to maintain complete closure of the auxiliary valve and opening of the main valve, with the result that vibrations and chattering of the valves would occur.

The introduction of a calibratedrestrictor between the intermediate chamber'andthe actuator, and preferably in the outlet of the intermediate chamber itself, gives rise to a second pressure-drop. This second pressure drop takes place downstream'lof the intermediate chamber as long as flow continues through the main valve towards the actuator. Consequently, this second pressure drop main} tains a substantial positive pressure in the intermediate chamber after the first triggering valve has been temporarily opened so as tokeep the auxiliary valve positively closed and the main valve open, however low the pressure between the restrictor and the actuator may be. The restrictor is preferably so calibrated that, it gives rise to a pressure-drop substantially equal to that through the main valve when fully open.'

Once the power stroke of the actuator is completed, fiow through the main valve and the restrictor ceases. The pressure in the intermediate chamber and in the actuator then becomes equal to the supply pressure thus ensuring that the auxiliary valve remains closed and the main valve open. The actuator is then maintained iri the fend of power stroke position until the second triggering valve is opened.

To facilitate rapid exhaustion of the actuator on the return stroke, the calibrated restrictor is preferably bypassed by a duct containing a non-return valve allowing flow in the exhausting direction only. This by-pass duct may contain a second calibrated restrictor, whose sole function is to stabilize the exhaust flow.

' Further objects of the invention will appear in the following detailed description with reference to the accorn panying drawing of one embodiment of the invention, given by way of example only and without implied limitationof the scope of the invention as defined in the hereto appended claims. v

In this embodiment the control 'device is unitary with a pressure source and an exhaust reservoir '4. .The pre's sure source is an hydropneurnatic accumulator-1 having a floating piston 2 separating the liquid spaceabove the piston from the penumatic pressure space'lt el'ow itQ T he control device itself comprises a body 25 on to the base of which the accumulator 1 is screwed and" on top. of which is mounted a casing, the interior of whichf'fo'rms the exhaust reservoir 4*. Chambersii and 31in the body 'termediate chamber 35.

25 are connected together by means of a passage 33 and communicate with the liquid space of the accumulator the'accumulator whenits pressure fhastallento alowe'r critical value. I I

' Chambers"3j1 and '21 respectively are closed from above by sub-'bodies'12 and 27 which are detachably fixed in the main body 25; and other sub-bodies 24 and one enhaust stroke of the controlled actuator 40. The main admission valve 6 is closed, the auxiliary valve 8 is open closing a chamber 37 are likewise detachably fixed in body 25. Theactuator 40 to be controlled is provided with a single service line 42 which enters the body 25 at'a service line opening 3,

The main'admission valve, constituted by a cone 6 lightly pressed towards its seating by a spring 7, controls seatable on the opening connecting chambers 35 and 39. a

The piston .is lightly spring loaded as shown in the :sense to unseatlthe valve member 8. .Ports 11 provide communication between the portion of chamber 39 below the piston 10 and the exhaust reservoir 4. A push-rod 9, extending irom valve member 8 through its seating, unseats the main valve.6 when the auxiliary valve member 8 is seated.

The auxiliary valve member 8 .is ,seatable to close the auxiliary valve and open the main admission valve 6 .by admitting hydraulic pressure to a chamber 14 above the piston v10. Chamber .14 communicates, via a side pipe, with chamber 37.

The first triggering valve, housed in subbody 27, is constituted by a ball lightly .springloaded towards its seating, which, when unseated, affords communication between chamber 21 and chamber 37, through a non-return'ball valve 22 .Ball 20 is unseatable by depressing an external push-button 17 against the elic t of a lightspring, .a loose push-rod .19 being interposed between the button 17 and the ball 20. When .ball 20 is unseated, the supply ,pressureof accumulator ,1 is transmitted, via the opening 29, passage 33, chamber21 and non-return valve 22 to thecharnber .14, causing piston 10 to be depressed to close the auxiliary valve 8 and open the main valve 6, a

The second triggering valve is constituted by a ball 16, lightly spring-loaded =towards its seating and unseatable by depressing art-external push-button 15 against the effort of a lightespring. When ball 16 is unseated chamber 14 communicates, via aside port 18 in sub-body 12 with the exhaust reservoir:4. a

The intermediate chamber 35 communicates with the serviceline opening 3 through a calibrated restrictor R located in a side port of sub-body '24. Theservice line opening 3 also communicates, through-a second calibrated restrictor r7,.1ocated in a :by-pass duct formed .in sub-body 24 and containing .a-nonvreturn' ball valve 23, with-the .in-

The non-return valve23 closes the ,by-pass duct against ilowlin the admission sense .indicatedby thelower arrow .to .the left of the service. line opening .3 while allowing how. in .the exhausting ,sense indicated by the upper arrow.

The .detachabilityffof lsubihody 24 enables the restrictors R and r to be exchanged .jfor .others having .different ratings without difiiculty.

and both triggering valves 15, 16 and 17-20- are closed. The intermediate chamber 35, being in communication via valve 8 with the chamber 3,? below the piston, is at exhaustpressure andso is :the chamber 1} above the piston owing to the intercommunication of chambers 14 and via chamber 37 and the restrictor 13 through which there is no flow, and consequently nopressure-drop, the piston 10 beingstatio nary. :Both facesuof piston 10 are therefore subjected .tothe exhaust pressure acting over equal areasand consequently valve 8 is held open by its spring. The device therefore remains in the normal position until thefirst triggering valve ball 20 is unseated by depressing the push-button 1.7.

As soon as 'ball 20 is unseated a substantial fraction of the supply pressure is immediately applied to the chamber 14 via the non-return valve '22, and since the underside of piston 110 is at exhaust pressure, descent of the piston under 7 the vpressure applied above it is substantially unresisted and rapid closure of valve v8 and opening of valve 6 is efiected.

During this phase, the restrictor 13 impedes flow of liquid from the chamber 37 to the intermediate chamber 35 and thus ensures that there is very little loss of pressurehetween the chamber 21, which is at the full supply pressure, and chamber 14. If the rcstrictor 13 were not there, the liquid flow through valve 22 would be by passed'direct to exhaust through the intermediate chamber '35 and piston ,10 would not be displaced.

'When the button 17 .is released, the spring loaded ball 20 is re-seated by "the spring and the supply pressure.

3 below it, and the pressure in chamber 14, acting .on piston 10 in the sense to 'keep the valve 8 closed, falls to that in the intermediate chamber 35 and in the absence of any displacement of piston 1'0 there can be no flow through restrictor 13 to ,hinder the equalization of the pressures in chambers 14 and 35. The pressure in cham- The drawing shows .thecontr olcdevicein the .normal her '35 is also applied directly to valve member .8 in the sense to open it; but since the area of piston 10 is intentionally made considerably greater than, and preferably about four times as great as, that of the seating of the valve member 8, the valve-closing effort of this pressure is predominant and the valve 8 will remain positively closed, provided the pressure in the intermediate chamber 35 is :sufiicient to'be effective.

Now, when valve -8 closes, valve 6 opens and admits liquid from the accumulator 1, via chamber 31, into the intermediate chamber 35 and thence into the service line 42 of the actuator 40, via opening 3. As long as flow in this sense is taking place there is a pressure-drop across the valve 6, but owing to the presence downstream of the inter'mediate'chamber 35 of the calibrated restrictor R through which the liquid must also flow and cause a further pressure-drop, the pressure-drop across the valve 6 only accounts :for part of the difiference between the supply pressure and that in the service line, which is initially at exhaust pressure; and consequently, from the instant at which the valve 6 opens, a positive pressure is established in the intermediate chamber 35, however low may be the pressure in'the service line.

The restrictor R is preferably calibrated to produce a pressure-drop equal to that across the valve 6 when fully open, in which case the pressure in the intermediate chamber '35,from the-instant at which valve '6 opens, can never be less than half the supply pressurerand this is adequate toensure that'the valves remains closed and the valve 6' open,-provided the net area of piston 10 (i e. its'total .area' less that of theseating of valve 8) is not too'sma'll.

"Premature release of the push-button Q17, before operating pressure, suflicientrto overcome the return "biasmeans of the actuator 41}, has beenrestahlished' in serv ce 1ine= 2r will therefo e not lead to ihI 9. l. ..-8! S1 chatteriua at valite tt 'an fi- Evidently, when the power stroke of the actuator 40 has been completed, flow through valve 6 and restrictor R ceases. Then, the pressure in the intermediate chamber 35 and in the actuator itself becomes equal to the supply pressure, thus ensuring that the valve 6 stays open and the actuator remains in its end of power stroke" position, until the push-button 15 is depressed to unseat the ball 16 and vent the chamber 14 to exhaust, while the restrictor 13 momentarily delays the concurrent release of pressure in the intermediate chamber 35, thus assisting the rapid opening of valve 8 and closure of valve 6. Once valve 8 has been opened and pressure on opposite sides of piston has been equalized at the exhaust pressure, valve 3 must stay open as previously stated. This allows actuator to be exhausted freely through both restrictors R and r, flow through the latter in this direction being permitted by the non-return valve 23. This completes the operative cycle of the device, the actuator remaining in the end of return stroke position until push-button 17 is again depressed.

it is to be understood that, within the scope of the invention as defined in the appended claims, the apparatus herein described and illustrated may be modified, improved, simplified or elaborated in respect of detail design, lay-out or otherwise, in any way that may be necessary and is within the normal competence of those skilled in the art.

What is claimed is:

1. Hydraulic control device for selectively controlling the connection of an hydraulic service line serving a single-acting hydraulic actuator to a hydraulic pressuresource and exhaust respectively comprising a valve chamber connected to the service line, a normally closed main valve controlling communication between the pressuresource and said chamber, a normally open auxiliary valve controlling communication between said chamber and exhaust, means actuated by said auxiliary valve to open positively said main valve when said auxiliary valve closes, said auxiliary valve being subjected when closed to the pressure in said chamber acting in the sense to open the auxiliary valve, a single-acting hydraulic cylinder and piston operative to close said auxiliary valve, said piston having a greater area than that on which the pressure in said chamber is exerted in the sense to open the auxiliary valve, a passage connecting said chamber to said cylinder, a restrictor in said passage, a first triggering valve for temporarily connecting said cylinder to said pressuresource, a non-return valve between said first triggering valve and said cylinder for preventing flow from said cylinder to said first triggering valve, a second triggering valve for temporarily connecting said cylinder toexhaust, and a calibrated restrictor between said chamber and the service line.

2. Hydraulic control device for selectively connecting an hydraulic service line serving an hydraulic actuator, such as a single-acting jack, to a source of hydraulic pressure and to exhaust respectively, such device com prising a valve chamber connected to the service line, a main valve controlling communication between the pressure source and said chamber and normally held closed by the pressure of said source, an auxiliary valve controlling communication between said chamber and exhaust and subjected when closed to the pressure in said chamber acting in the sense to open it, a singleacting hydraulic jack operative to close the auxiliary valve and open the main valve, the piston area of said jack being considerably greater than the area of the auxiliary valve on which the pressure in said chamber acts, a duct interconnecting said chamber with said jack, a restrictor in said duct, a normally closed triggering valve controlling direct communication between said jack and exhaust, another normally closed triggering valve controlling direct communication between the pressure source and said jack, a non-return valve preventing flow from said jack to said other triggering valve, and a calibrated restrictor through which said chamber communicates with the service line.

3. Device as defined in claim 2 including a bypass duct connecting said chamber to the service line and a non-return valve in said by-pass duct preventing bypass flow from said chamber to the service line.

4. Device as defined in claim 3 including further a calibrated restrictor in said by-pass duct.

5. In combination with a device as defined in claim 2, a hydro-pneumatic accumulator constituting the pressuresourceand an exhaust reservoir, said device, said accumulator and said reservoir being assembled as a unitary structure.

6. The combination defined in claim 5 including means for re-charging said accumulator from said exhaust reservoir.

7. Hydraulic apparatus for operating and controlling a single-acting hydraulic actuator comprising a main body having an external opening for connection to the actuator, a hydro-pneumatic accumulator secured in a fluidtight manner to one end of said valve body, the latter constituting a closure member of the liquid chamber of said accumulator, a casing constituting an exhaust reservoir fluid-tightly secured to the other end of said body, a first valve sub-body detachably mounted in a first pocket of said main body, a second valve sub-body detachably mounted in a second pocket of said main body, passages in said main body connecting both said pockets with the liquid space of said accumulator, a third subbody detachably mounted in said main body, a chamber formed in said third sub-body, said main body and said first sub-body, two ducts formed in said third sub-body connecting said chamber to said external opening, a calibrated restrictor in each of said ducts and a non-return valve in one of them preventing flow from said chamber; in said first valve sub-body an opening constituting a main valve seating and connecting said first pocket with said chamber, a movable main valve member subjected to the pressure in said first pocket in the sense to apply it to said main valve seating, a cylinder communicating with said chamber through an opening constituting an auxiliary valve seating, said main and auxiliary valve seatings being opposite one another, a piston slidable in said cylinder and having an area greater than that of said auxiliary valve seating, an auxiliary valve member rigidly attached to said piston and seatable on said auxiliary valve seating, a push-rod extending from said auxiliary valve member through its seating, with clearance, and engageable with said main valve member to unseat it when said auxiliary valve is seated, a port connecting the space in said cylinder on the same side of said piston as said auxiliary valve member with the interior of said exhaust reservoir,duct means connecting said exhaust reservoir with the space in said cylinder on the opposite side of said piston to said port, a ball valve normally obstructing said duct; duct means inter-connecting said chamber with said last-named cylinder space, a restrictor in said last-named duct means; other duct means connecting said last-named cylinder space'with a port in said second valve sub-body, a non-return valve in said other duct means preventing flow towards said last-named port; in said second valve sub-body a normally closed ball valve controlling communication between said second pocket and said last-named port, and separate means for temporarily opening each of said ball valves, each of said last-named means including an externally accessible push-button.

References Cited in the file of this patent UNITED STATES PATENTS 1,961,465 Thompson June 5, 1934 FOREIGN PATENTS 594,222 Germany Mar. 14, 1934 1,145,495 France May 6, 1957 

